Q: How do you know if you’re getting enough vitamin D from the sun?

A: If you are getting 10 to 15 minutes of sun on your legs and arms each day in good sunlight, you’re getting enough to get you to 1,000 international units (IUs) per day. Of course, the actual amount will vary based on the weather, season, latitude, altitude, sunscreen, the amount of skin exposed and the color of your skin, but that is a good rule of thumb. People who live in the northern states probably should take a vitamin supplement and eat foods that are rich in vitamin D except for the late spring and summer seasons when their skin could make enough.

In the July 2008 issue of Communicating Food for Health, the cover article shared information on an analysis of 18 randomized controlled clinical trials that showed that vitamin D supplements may significantly reduce the risk of dying from all causes combined. The current government guideline for the vitamin D requirement is based only on the need for vitamin D to prevent bone disease.

According to the research being studied, that level may not be adequate to meet all other metabolic functions that utilize vitamin D. Low levels of vitamin D apparently impair immune function and increase the risk of at least several types of autoimmune diseases, including multiple sclerosis, rheumatoid arthritis, psoriasis and type 1 diabetes.

The article suggests that individuals really should get their 25-OH- D level checked, and if it is below 30 nanograms per milliliter, they should visit with their physician about taking 1,000 IUs of vitamin D3 supplement per day. Most multivitamins have 400 to 600 IUs, so people taking a multivitamin can often get enough when they are also consuming fortified milk or soy milk and fatty fish like salmon, tuna and mackerel. The current adequate intake amount for vitamin D is about 200 to 400 IUs per day for most adults, 600 IUs per day for older adults (71 years and older) and 200 IUs for children. But the American Academy of Pediatricians doubled the amount for kids based on new research, and the amounts for adults is likely to be revisited soon because of similar findings.

Q: What other foods are good sources of vitamin D?

A: Here is a listing of common heart-healthy foods that contain at least 10 percent of the recommended daily value for vitamin D: bluefin tuna, cooked (4 ounces) – 1,061 IUs; sockeye salmon (4 ounces) 739; skipjack tuna, cooked (4 ounces) 586; Atlantic salmon (4 ounces) 346; sardines canned in oil (4 ounces) 250; mackerel, cooked (4 ounces) 242; herring or trout, cooked (4 ounces) 240; tuna, canned yellowfin (4 ounces) 161; shrimp (4 ounces) 160; nonfat skim milk (1 cup) 100; fortified orange juice (1 cup) 90; fortified rice/soy beverage (1 cup) 80; canned tuna (4 ounces) 63; cod (4 ounces) 60; fortified cereal (1 cup) 40.